This proposal is focused on integrating comparative genetics and molecular evolution with functional neurobiology as a means of generating a better understanding of human neuropsychiatric and addiction disorders and developing better animal disease models. This will concentrate initially on monoamine oxidase A (MAOA). MAOA has been associated with neuropsychiatric and addiction disorders including alcoholism, depression, and autism among others and is a target for widely prescribed anti-depression and anti-anxiety medications. MAOA is also hypothesized to have undergone positive selection in humans since the divergence from chimpanzees but harbors a regulatory polymorphism that is functionally homologous between humans, apes, and certain old-world monkey species. Understanding differences in MAOA function in humans may lead to better understandings of the causes of its associated neuropsychiatric disorders and allow for the development of more appropriate genetic models of these diseases in non-human primates. Here we propose to catalog the complete MAOA locus across primate species, including polymorphic variation in the more commonly used biomedical model species. We then propose to functionally investigate the consequences of these differences, as well as the functionality of ancestral sequences, in vitro. We will also assess the effects of polymorphic variation from non-human primates ex vivo and in vivo through measurement of mRNA levels and neurochemical concentrations in cerebrospinal fluid and neuroendocrine effects in blood plasma. Finally, we will integrate MAOA genotypes into existing alcohol self-administration studies in rhesus macaques to elucidate this genotype/phenotype relationship and develop better genetic models of alcohol use disorders. Through this work, a better understanding will be gained of the relevance of molecular evolution and comparative genetics to functional neuroscience and the study of human neuropsychiatric disease. Specifically, this work will elucidate if specific psychiatric disorders or symptoms are unique to humans resulting from human-specific genetic changes and the extent to which and ways that these psychiatric disorders and their treatment can be modeled in other organisms, particularly non-human primates. This will allow a better integration of the two fields and allow researchers to leverage the power of molecular evolution and comparative genetics to greater effect in studies of human disease going forward. It will also allow scientists to refine candidate gene analyses and better place into context animal models of neuropsychiatric disease.